1. Field of the Invention
The disclosed embodiments of the present invention relate to an image processing method, and more particularly, to a method for performing color interpolation upon images captured by an image sensor and related image processing apparatus thereof.
2. Description of the Prior Art
In any consumer electronic product using a single image sensor to capture images (e.g., a digital camera, a video camera, a multimedia mobile phone, a surveillance system, a video phone, etc.), the image sensor records red, green and blue color information through the Bayer color filter array covered on the single image sensor, wherein the image sensor only records one color intensity value for each pixel location to reduce the manufacturing cost. Further, in order to restore a raw Bayer CFA image captured by the single image sensor to a full-color image, there is a need for a color interpolation process to obtain the missing color data. Since the color interpolation algorithm includes analysis of the structure and color of the image content, it has a great impact on the image quality of the final output.
In the field of IC designs, color interpolation usually occupies a lot of space of line buffers, and the computational complexity of the color interpolation is relatively high. Therefore, how to reduce the manufacturing cost under the premise of effectively preventing distortion, including zipper effects, color aliasing, Moire pattern and false color, from emerging on object boundaries and texture regions of the image has become an issue to be addressed in this field. In addition, Taiwanese Patent Publication No. 1274908 discloses using a pre-calculated minimum square error (MSE) to estimate the weighting factors of the color pixel values of the neighboring pixels to be used. Besides, another technique disclosed in Taiwanese Patent Publication No. 1296482 is to detect image edges on a plurality of interpolation directions for a target pixel and generate a plurality of image edge gradients, and then estimate the missing color ingredients of the target pixel according to a sum of normalized random adjustment factors. However, the above techniques require a larger memory buffer and a considerable number of division operations, thus leading to an increased manufacturing cost and making the hardware implementation not easy to realize. As a result, the practicality of these techniques is reduced. Furthermore, the above-mentioned color interpolation method refers to excessive direction information, and thus introduces the blurring effect and reconstruction distortion to image areas of sharp edges and fine structures easily, which reduces the image quality.